Phenolic compounds in wholegrain rye and its fractions

Abstract

Rye (Secale cereale L.) has traditionally had an important role in the daily diet especially in Northern and Eastern Europe, and in addition to dietary fibre, rye grain is a good source of various phytochemicals in our diet. The focus of the present work was to find out how various phenolic compounds are distributed in rye grain fractions prepared by air-classification, and compare rye brans produced by different separation techniques (sieving or air classification). Of the phenolic compounds, phenolic acids were analyzed as organic solvent soluble (OSS) free, esterified and glycosylated residues, organic solvent in-soluble (OSI) esterified and etherified residues and OSI ferulic acid esterified to water extractable fibre. In addition alkylresorcinols, flavonoids, hydroxamic acid DIBOA (2,4-dihydroxy-1,4-benzoxazin-3-one), flavonoids and lignans were analyzed. Based on the determined concentrations, alkylresorcinols formed the most dominant group of OSS phenolic compounds in rye and its fractions, followed by smaller amounts of OSS esterified phenolic acids and hydroxamic acid DIBOA. In wholegrain rye and rye fractions, the major part (86–92%) of the total amount of phenolic acids was present as OSI-form bound to the fibre complex either via ester or β-aryl ether bonds. All of the analyzed phenolic compound groups were enriched in the bran fraction, which encourages usage of this part of rye grain in foods. The content and profile of phenolic compounds did not differ much between the two differently produced rye brans.